Today there are many requirements for "clean rooms" or clean areas which are free from dust or free from many other kinds of contaminants. Clean rooms or non-contaminated areas are needed to provide enclosed space which is: (1) free of bacteria for operating rooms, (2) free of contaminants or dust for use in industry for special manufacturing requirements, or (3) free of biological, chemical, and nuclear fallout contaminants for noncontaminated areas or structures used by the military services.
Airlocks or purge chambers are usually arranged so that a person or persons may enter the airlock, close the door, and remain there while fans provide a change of air. Then, when the air is sufficiently clean, the person or persons may open the door into the inner chamber or clean room and enter it without also allowing contaminated air to enter this inner chamber. However, there is much room for improvement and increased efficiency in the design of existing airlocks. One big drawback in existing designs is that airlocks, like most other conventional rooms or enclosures in buildings, are usually shaped so as to have a rectangular or square floor plan. Examples of such airlocks are those shown in U.S. Pat. Nos. 3,766,844 to DONNELLY, et al., 4,137,831 to HOWORTH, and 4,375,735 to RHOADS. Ideally, an airlock would function best with perfect mixing of the purge airstream and the contaminated air. Because of the rectangular or square cross sections of these airlocks, however, high contamination levels can continue to exist near the walls and in the corner of the airlock. The net result is a long period of time to purge an airlock of contamination. An additional problem is in the door designs. Airlocks in use today have doors that are either hard to use or can cause excessive amounts of contamination to enter the airlock.
Another type of airlock structure is shown in U.S. Pat. Nos. 3,501,213 and 3,576,206 to TREXLER. This type of airlock has a complex design providing a sterile locker or anteroom with a pair of entrances which are sealed by troughs or reservoirs of fluid. This arrangement appears to be effective but also is heavy and expensive to build. Obviously, it would not be suitable for a portable airlock.
A type of prior art device which functions to prevent contamination of a clean room is an air-curtain installation. Examples of this type of device are shown in U.S. Pat. Nos. 3,608,468 to McCLURKIN and 4,074,620 to JANSSON. These devices provide an air curtain or air barrier in a doorway or opening in a wall to prevent air flow through the opening. They appear useful for preventing cold air from entering a heated area but do not appear to be highly effective in preventing contamination of a clean room or a noncontaminated area. They also have the disadvantage of being expensive, heavy, and not suitable where a portable airlock device is needed.
U.S. Pat. No. 4,438,966 to HASTINGS discloses a round circular booth. However, this device is used to provide security, namely, a secure transaction interface with another room where money, valuables, or secure information are kept. This patent does not disclose or suggest a system capable of removing contaminated air from the booth in order to prevent contamination of the inner room.
It is, therefore, a general object of this invention to provide a more efficient method and apparatus for personnel entry/exit into and from a structure that operates in an ambient environment contaminated by toxic chemical agents while providing a clean, noncontaminated environment to the personnel inside the structure. It is another object of the invention that this entry/exit must be accomplished as expeditiously as possible without introducing the contamination from the exterior ambient environment into the protective structure.